Hey it's me Destin. Welcome back to Smarter Every Day. Today we're gonna do awesome science with
Orbix Hot Glass here at Lookout Mountain Alabama. Goggle up.
Science is about to happen. We're gonna use a high speed camera and learn about Prince Rupert's Drop.
[whispers] It's never been done on the internet. You're gonna learn something.
Let's go.
OK we are here inside the shop with
Cal. Cal owns the place. Can you show me how to make a Prince Rupert's Drop?
(Cal) Sure. I'm gonna gather some glass, drop it in a bucket of
cold water.
[sizzling sound]
(Destin) So after it cools down, this is what you're left with.
It kinda looks like a tadpole, but it has some really interesting mechanical properties.
We can actually hit this thing with a hammer and it won't break.
OK I'm ready. [bang] Didn't go.
OK I think Cal is kind of a pansy so I.. You think you can break it? [laugh]
So we're gonna try again only this time I'm gonna make him hit it really hard
and I'm gonna record it with high speed. Does that work? Think you can break it? Alright. Let's do it.
The challenge is on. (Cal) Just hit it? - Yep.
[bang] [shattering] [laughs] So do you think you actually broke it? I don't think
you did. You think you broke it? - I know I broke it. [laugh]
- Let's look at the high speed.
[music]
OK so the drop broke, but technically it wasn't the
hammer that broke it. If you look close in the high speed you can see that it's the wiggling of the
tail that makes it go. This is the mystery of the
Prince Rupert's Drop. You can try
as hard as you can to break the bulb, but you can't.
But, if you even nick the tail, the entire thing will explode. Not shatter,
but actually explode. Let's go outside and I'll show you more.
OK we're gonna just run an obscene frame rate here. We have this
Phantom V1610. So, glass breaking occurs
so fast that you have to have like hundreds of thousands of frames per second, so we're gonna
have a lower resolution and we have to have a lot of light as well. We're also gonna use this Miro over
here to run about 3000 frames per second so we can get a wide shot to see the whole event.
as well. 3..2..1.. go.
[shatter]
[Awesome Music by Gordon McGladdery}
OK now we understand what a Prince Rupert Drop does, but at this point
we don't quite understand why it does it. Let's take a closer look.
OK this is called a polariscope and basically what it is is it's a filtered piece of
glass that's polarized. I have another filter here. You can see if I turn it,
then I can block out the light. Now if I put this on the camera
that you're looking through here, and then I put the Prince Rupert's Drop in between
the two pieces of glass, you should be able to see the internal stresses built up
inside the Prince Rupert's Drop. So to understand how these stresses got here, let's
use the color grey to represent nice and strong solid glass. We use red
to represent molten glass and because of the thermal expansion coefficient it's safe to assume that the
higher the temperature the larger this glass wants to be. Blue represents glass that's cooling
off, or transitioning between the two states. Because of that same thermal expansion coefficient
this glass is shrinking and basically pulling in on itself. Think of a
Prince Rupert's Drop as a bunch of little infantessimal pieces of glass with each piece trying to interact
with the pieces around it. When the molten glass is first dripped into the water, the
outside layer touches the water and immediately solidifies. This locks in that
outside shape of the drop. The inside of the drop however is still a hot expanded
liquid. As heat's transferred to the water that glass on the inside slowly begins to
cool down, and pulls in against that outside layer. The problem is that
because it's already locked in as a round solid, it only compresses tighter against
itself. This actually makes it stronger. Kind of like how an arch compresses and gets stronger when
you put your weight on it only this is in all directions. And because the cooling glass can't
move that outside layer it begins to pull against itself, causing it to be
in extremely high tension. It then hardens in this state of tension and there you have it, a
Prince Rupert's Drop. The outside is in extremely high compressive stress and the inside is in
extremely high tensile stress. If one link in this tension chain is ever cut, it
breaks on down the line, feeding off of its own stored up energy just like a chemical
explosive does. The difference here is that instead of releasing chemical potential energy
mechanical strain energy is released. This wave of energy is what we call a
failure front. You can directly measure the velocity of that failure front as long as
you have a camera fast enough. Let's give it a shot at 130,000 frames
per second. 3..2..1..go.
Got it?
[music]
So a big thanks to Cal from Orbix Hot Glass. If you found this
interesting and you want to support him by buying stuff go click on the link, wherever I
put it, and go check out his web site. Click the cat to subscribe.
With the helmet. [laugh] It's a sad looking cat.
You've never caught the cat on fire, ever? - Never. - Not even once?
- Never. - These things are named for a guy named Prince Rupert, imagine that,
who lived in Bavaria back in the 1600s. Here, here.
[shins banging on concrete laughter through pain]
He brought these over as a gift to King Charles II in England who gave them to his
Royal Society to try to figure out. Yep ready. [clang]
Holy smokes!
- Aah the tension's killing me. [shatter] -(Destin in background) NO DON'T BLOW UP!
- You know it blow.. blowed up? - Yep, it blowed up.
- It BLOWED UP Y'ALL! [laugh]
Captioning in different languages welcome. Please contact Destin if you can help.
[ Captions by Andrew Jackson ] captionsbyandrew.wordpress.com